1. Field of the Invention
The present invention relates to an ultrasonic imaging system and more particularly, relates to an imaging system including a single filter module filtering an analog sub-array beam signal and performing digital beamforming.
2. Description
The technique of generating images by means of ultrasound has been widely applied to people's life due to the development of science and technology. Compared with medical imaging systems such as X-ray, CT, MRI and nuclear medicine imaging utilized in clinic, ultrasonic imaging has advantages of competitive price, non-invasiveness, radiation free, instant imaging, spatial resolution of centimeters in images, portability, flow estimation ability, etc. Thus, ultrasonic imaging is commonly applied to clinical diagnosis in every medical category.
The principle of ultrasonic imaging is to reconstruct an image of an object to be detected with the characteristics of diffraction and reflection of sound waves. When ultrasonic imaging is utilized in flow velocity estimation, since signals of flow velocity are weaker, signals of a motionless object need to be filtered via a filter in order to obtain a precise result of flow velocity estimation. However, traditionally a clutter filtering is performed on signal via analog or digital method, i.e. analog clutter filter or digital clutter filter. With digital clutter filtering, signal distortion may occur due to quantization error and a large amount of digital hardware resource is required for data storage and signal processing; with analog clutter filtering, beamforming is forced to be done via analog method so that advantages of programmability and precision of digital beamforming are missed.
Besides, a multiple-gated flow velocity estimation is required when users hope not to lose range images of the flow velocity estimation. However, since signals sent and received have to be temporarily stored for the multiple-gated flow velocity estimation and since Doppler gates with the same range have to be found for the calculation of flow velocity, several clutter filters are required for calculating simultaneously in different range of the Doppler gates in order to speed up imaging. As a result, costs on scratchpad memory and computing of hardware are considerable.